Textile composites are being considered for use in aerospace primary structures as they have the potential to reduce the cost of manufacturing composite structures. Non-Crimp Fabrics (NCFS) are one class of textile composites which are being investigated for this use. The aim of this project was to determine what affect the fabric structure of the NCF has on the larninates microstructure and in turn what affect this has on the final mechanical properties. After an explanation of the need for textile composites a review of the advantages and disadvantages of the different classes is presented. The concept of a link between the microstructure of the composite and its mechanical properties is introduced with a review of past work in this area. Image analysis methods are identified as the most promising microstructural measurement techniques and their past use in quantifying composite microstructures is surveyed. Methods of quantifying the tow crimp, resin rich areas and fibre orientations were developed using image analysis techniques. These methods were then used to quantify the microstructure of a wide range of NCF laminates, with woven and unidirectional materials being studied for reference. It was found that the initial structure of the NCF had an influence on the final nicrostructure of the laminate. Both the amount of tow crimp and resin rich areas were affected by the spacing of the tows, stacking sequence, stitch density and stitching material. It was also shown that the fibres inside the tows had large orientation variations across their cross-section. The mechanical properties of the materials wer'e evaluated by compression and Interlaminar Shear (ILS) testing. It was found that that an increase in the tow crimp reduced the compression strength while an increase in the resin layer thickness decreased the IS strength. It was shown that these results agreed with past experimental and modelling work.